Cardiac - Hemodynamics Flashcards
What is the source of pressure on the systemic side of the cardiovascular system?
LV
What is the source of pressure on the pulmonary side of the cardiovascular system?
RV
What causes the pressure differences acoss the body?
Gravity
What happens to pressure when a person is standing upright?
Above the heart: BP is higher
Below the heart: TP is higher
What happens to pressure in the body when a person is laying down?
BP and TP are equal throughout the body
What is the most compliant part of the arterial system?
Thoracic Aorta
What is the most compliant part of the venous system?
Vena Cava
When are vessels most compliant?
At their lowest volume
Why is the venous system so compliant?
It is high volume and low pressure
What is the equation for compliance?
Compliance = change in V/Change in P
What happens to compliance when you increase sympathetic tone of the veins?
Compliance decreases
What happens to resistance when you increase sympathetic tone to the Arterioles?
Resistance increases
Aortic pressure increases
What effect does venoconstriction have on cardiac output?
Venoconstriction -> increase sympathetic tone -> increase NE -> decrease compliance to vena cava -> Increase pressure to vena cava -> Increase venous return -> increase preload/EDV -> increase SV -> increase CO
What effect does age have on compliance?
Compliance decreases
How are cross sectional area and velcoity of flow related?
The are inversley related
Decrease cross sectional area -> Increase velocity of flow
When is diffusion most effective?
With low volume flow and high cross-sectional area
In a vein oriented upstream of blood flow…
Total pressure is measured
Blood flows directly into tube
In a vein oriented at a right angle to the direction of blood flow…
Only lateral componant is measured
What happens to velocity of blood flow if you have plaque by the entrance to your kidneys?
Velocity of blood flow increases as it flows past plaque -> reduced renal blood flow
Lateral component of pressure will decrease at site of plaque
What happens in a heart with aortic valve stenosis?
Leafelets cannot open all the way
Velocity of flow increases -> less perfusion -> less blood flow during distole -> less nutrient blood flow
Where is the main place resistance is regulated?
The arterioles
Constriction ___ resistance
Increases
Dilation ___ resistance
Decreases
What influences volume flow?
Pressure
Length of tube
Radius of tube
Viscosity of the liquid
When is Poiseuille’s Law applicable?
No variations in flow
Flow is laminar
The fluid is newtonian fluid
Flow through a tube depends on…
Inflow and outflow pressures
What is the relationship between pressure and volume flow?
They are directly proportional
When pressure doubles, volume flow…
doubles
When the pressure difference decreases, flow…
Decreases
Preasure is equal when flow…
is nonexistant
If the tube length doubles, flow…
decreaaes by 50%
What is the relationship between the length of the tube and volume flow?
They are inversely related
If the radius of the tube doubles, flow…
Increases
What is the relationship between radius and flow?
They are directly proportional o
If viscosity doubles, flow…
decreases by 50%
Blood flows faster…
in the center of the vessel
When hematocrit increases, viscosity…
increases
Whatr is the equation for Poiseuille’s Law?
Q = pi(Pi - Po)r^4/8nl
When the arterioles constrict…
Radius decreases -> volume flow to capillaries decreases -> pressure in the aorta increases
When the arterioles dilate…
Radius increases -> volume flow increases
Where is the greatest change in pressure found?
Arterioles
In the circulatory system, resistance circuts are in….
parallel
Why is it important for resistance circuts to be in parallel?
It allows the divertio of blood flow to different areas of body based on need
What happens o the resistance in a circut when more resistors are added?
It gets reduced
What is the equation of mean arterial BP?
Diastolic pressure + 1/3PP
During systole…
blood is ejected into the aorta
Pressure is lowest during…
diastole
When does PP increase…
As you move away from the heart due to decreased compliance
BP =…
CO * TPR
Increased TPR ___ BP
Increases
Increased CO, and constant TPR ___ BP
Increase
Increased TPR, decreased DP ___ CO
Decrease
What happensto transmural pressure when a subject is laying down?
TP in the foot, heart, and head are essentially the same because gravitational effects on the circulatory system are equal
What happens to transmural pressure when a subject is standing?
TP above the heart decreases and below the heart increases
Below the heart TP is greater than BP
Above the heart TP is less than BP
Compliance =….
Change in V/Change in P
What does it mean that the compliance of an organ or vessel can be altered by changing the mechanical properties of the walls?
SNS stimulation of veins will increase contraction of smooth muscle in the vessel wall, making the wall more rigid, reducing compliance of the vein
velocity of blood flow (v) =
Q/A
Where in the cardiovascular system is there a high cross sectional area and low velocity flow?
In the pulmoonary circulation and in the capillary beds where exchange is very important
What are the two components that make up pressure of flowing blood?
Lateral or static pressure
Kinetic energy of flowing blood or the dynamic component of pressure
What effect does aortic stenosis have on the cardiovascular system?
In this condition the entire output of the LV must pass through a narrowed (stenotic) valve orifice. Since the cross-sectionl area through which the blood must flowis greatly reduced, the flow velocity is increased. The kinetic pressure is high but the lateral or static pressure is markedly reduced
With non-turbulent laminar flow, the flow rate is proportional to…
The pressure gradient
___ is one of the principle determinants of the rate of flow.
Pressure
What is the principle determinant of reistance to blood flow thorugh any vessel in the cardiovascular circulation?
Radius
With the arrangement of resistances in parallel the total resistance will be ___ the resistance of any of the individual components.
Less than
Why is it important that the circulatory system is arranged in parallel?
Resistance can be altered in one vascular bed without effecting the flow in others
Large changes in resistance on one vascular bed has minimal effect on TPR and energy requirement from the heart
Flow to “nonessential” vascular beds can be redirected to others to reduce resistance
